Regions
Banff Yoho Kootenay.
Building hazard with flurries & wind tonight and Thursday. The new snow will be great for ski conditions, but will make for touchy avalanche conditions as it lands on a weak base.
Weather Forecast
Flurries will continue tonight, expect up to 10-15 cm. After a break on Wednesday, flurries return for Thursday where another 10-30 cm may fall by Friday evening. The greatest amounts will be west of the divide. Temperatures should remain cold throughout, winds will be moderate to strong W/SW during each snow event.
Snowpack Summary
Up to to 10 cm of new snow has fallen so far. Its buried a widespread weak layer of surface hoar/facets and is building new wind slabs with moderate SW winds in the immediate lees. The new snow will sit on a generally weak snowpack, with the October 26th crust/facet layer being up to ~30 cm above ground. Snow depths range from 50-85 cm at 2000 m.
Avalanche Summary
No new avalanches reported or observed today, but as recently as Saturday someone triggered a nasty looking size 2 on the SE slopes of Cirque Fore-Peak at 2700m above Helen Lake. Two skiers were caught on the flanks of a slab 20-40cm deep, 80m wide, running up to 250m with no burial but they some lost equipment.
Confidence
Intensity of incoming weather systems is uncertain
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.